Lateral unicompartmental knee arthroplasty with mechanical instrumentation : tips and tricks to guarantee excellent long-term outcomes

Background: Lateral unicompartmental knee arthroplasty (UKA) is performed significantly less frequently than medial UKA, primarily due to the lower prevalence of valgus deformities. Despite potential benefits, many surgeons prefer total knee arthroplasty (TKA) due to historical concerns regarding revision rates, component dislocation, and disease progression in adjacent compartments.

Objective: This article provides a technical update on lateral UKA, detailing surgical indications, operative strategies to optimize outcomes, and long-term clinical results from a multicenter retrospective study.

Key Points: Successful lateral UKA requires an intact anterior cruciate ligament and reducible valgus deformity, typically under 15°. Surgical technique emphasizes a lateral parapatellar approach without ligamentous release to avoid overcorrection. Precise tibial component positioning in internal rotation and slight valgus is critical to prevent femoral impingement and edge loading. Data from 268 lateral UKAs with a mean 9.1-year follow-up demonstrated a 10-year survival rate of 85.4%. The primary cause of failure was osteoarthritis progression in other compartments (n=26). No significant differences in survival were observed between resurfacing and cutting-block implants or between cemented and cementless fixation. High patient satisfaction (94.3%) and excellent functional scores were reported, particularly in elderly populations.

Conclusion: Lateral UKA is a reliable procedure for isolated lateral compartment disease when strict indications and precise surgical techniques are followed. Long-term survival and functional outcomes are comparable to TKA, offering a bone-preserving alternative with high patient satisfaction.